According to the prior art, such methods are already being employed for manufacturing plastic containers. U.S. Pat. No. 3,675,521 e.g. shows a device in which bottles comprising a double neck shoulder are cut by means of a knife underneath the neck shoulder such that a wide-mouth bottle for beverages is formed.
WO 2004/009331 A1 also describes a method and a device for the manufacture of a wide-mouth plastic bottle, where first a plastic bottle with a narrow neck and a thread impressed in the central area is formed by means of a stretch blow process. The final wide-mouth container is formed by cutting the intermediate by means of knives above the impressed thread, so that the upper mouth or neck region of the intermediate is omitted.
ES 2253110 also shows a method for the manufacture of a wide-mouth plastic bottle, here, too, first an intermediate being formed by stretch blowing. This intermediate is cut by means of a knife movable along the longitudinal axis of the container at an impressed shoulder.
It is common to all three mentioned prior art methods that the cutting operation is carried out by means of a knife, so that only containers of a certain wall thickness can be handled. If the wall of the containers becomes too thin, a faultless performance of this method is no longer possible as the container formed is too instable to resist such a mechanical intrusion as that of the knives. Another problem with this prior art is that wear of the cutting knife has to be expected, so that on the one hand the quality of the packaging containers formed decreases as the period of application of the knives increases, on the other hand the cutting knives have to be replaced relatively often. A further disadvantage of the known methods is that the mechanical cutting operation by means of the knives cannot be arbitrarily extended with respect to the cutting speed.